High frequency electric circuit modeling for transformer frequency response analysis studies

• Published in: International journal of electrical power & energy systems Vol. 111; pp. 351 - 368
• Main Authors: Zhao, Xiaozhen, Yao, Chenguo, Abu-Siada, Ahmed, Liao, Ruijin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2019
• Subjects: Fault diagnosis; Frequency response analysis; High frequency electric circuit model; Power transformers; Fault diagnosis; High frequency electric circuit model; Frequency response analysis; Power transformers
• DOI: 10.1016/j.ijepes.2019.04.010
• ISSN: 0142-0615

•An improved model for power transformer frequency response analysis studies is proposed.•The proposed model is aimed at understanding the impact of various mechanical fault types and levels on the power transformer frequency response signature.•A standard code for FRA interpretation can be established.•The accuracy of the proposed improved model is assessed by comparing its FRA signature with that of a power transformer hardware model during healthy, short circuit disks, radial deformation and axial disks buckling faults. Power transformers are subject to winding and core deformations due to short circuit faults and other environmental conditions. Majority of these faults are of progressive nature and should be rectified as soon as they emerge. Frequency response analysis (FRA) has been widely accepted as a reliable diagnostic tool to detect such faults. As reliable interpretation codes for FRA signatures have not been fully developed and accepted yet, researchers have put much effort to investigate the impact of various mechanical deformations on the transformer FRA signature. Because of the intrusive nature of such faults when staged on a real transformer, most of the studies in the literatures were conducted on a transformer high frequency electric circuit model. Simplifications assumed in these models by ignoring the turn-to-turn capacitance, not taking into account the detailed winding structure and not considering all mutual inductances between coils in various phases have reduced the accuracy of the obtained results. To establish reliable FRA interpretation codes, it is essential to develop electric equivalent circuit models that can yield FRA signature as close as possible to the FRA signature trend of the real transformer. This paper proposes a detailed transformer high frequency electric circuit model which considers the winding structure, inter-turn capacitance and all mutual inductances. Calculation details of the model’s parameters are presented. The accuracy of the proposed model is assessed by comparing its FRA signature with that of an equivalent transformer hardware model during healthy, short circuit disks, radial deformation and axial disks buckling fault.